Automatic telephone system



Jan' 3, .1939 E. s. PETERSON Er AIL 2 2,142,652

AUTOMATIC TELEPHONE SYSTEM Filed March 6, 1936 5 Sheets-Sheet 1 1 2a Q E I l mi ATTORNEY.

Jan. 3, 1939. E. s. PETERSON -Er AL.-` 2,142,652

y AUTOMATIC TELEPHONE SYSTEM Filed March e, 193e 5 sheets-sheet'z INVENTORS EDWARD s, PETERSON ,BY NORMA/v H. .SAL/M0525.

ATTORNEY.

Jan. 3, 1939.` E. s. ETERSON mL, 2,142,652

AUTOMATIC TELE-PHONE SYSTEM Filed March e, 1936 s sheets-sheet 5 hmll .IJIDI uw SN.

N w. mh. H P a D M n W w NORMAN H. SAUNDERS ATTORNEY.

Patented Jan. 3, 1939 UNiTEo syrAfrEs.

einen PAfrELNT oFFicE.

AUTOMATIC TELEPHONE SYSTEM aware Application March 6,

' v2o claims.

The present invention relates in general' to automatic telephone systems and more inA particular to small automatic systems which are adapt# ed for use in rural communities or other situations involving a limited number of subscribers.

In a situation of this kind it is often desirable to have the subscribers stations equipped withI ordinary manual telephones, which may .be vof the local battery magneto type, and to provideA for the control oi the automatic switches from some remote point, generally a city exchange, where operators are available. The auto-matic system which forms the subject matter of this invention is of the foregoing character, and the object of the invention, therefore, may be stated as the provision of anew and improved remotely controlled community automatic exchange, com-I monly known as an R, C. X.

The invention will be described hereinafter with reference to the accompanying drawings7 in which there is shown by means oi the usual circuit diagrams sufcient of the equipment involved to enable the invention to be explained and un derstood. f

Referring to the drawings, a subscribers stal' tion'is shown at A, Figflywith a line-23 extending to the exchange, or R. C. X., where a line relay 4 is provided; A similar station B is indicated in Fig. 2. There may be a total oitwentytwo subscribers lines connected to the exchange.

Connections between-the subscribers lines are established by means of link circuits, each including a nder for connecting with calling lines .and

a connector for extending connections to called lines. One of these link'circuits is shown in Figs.

l and 2 of the drawings, and comprises the .finder F, Fig. l, and the connector C, Fig. -2, together with the relays and circuitfconnections zshown. The finder F and connector-'C may be single mo.- tion rotary switches having "twenty-five sets .of contacts each. Of course larger switches Ycould be used and the capacity ofthe system'would be correspondingly increased. The number of-flink circuits provided depends on tra-flic requirements. Usually three or four links will sunlce ioran ex-` change of twenty-two lines. i

The subscribers lines are connected in multiple through the banks of all the finders and connectors. Thus in the'case of the. lineof -station A, the drawings show the connections of thisline in the banks of nder F and-itlwill'be understood that the line is similarly1 connected in. the banks ofthe other iinders.. Thefdrawings also show the line or" stationA'as having `a `set of socalled normal conductors Which extend to the connector banks and are so labeledv in the drawr ings. The line of station B is connected `the same way, as are vthe'vother lines V,in the system. i f The connectors such as'C have to bedirectively operated in accordance with-'the ifnumbersl of 193e, serial No. 67,442 (ol. 17e- 26) called lines,` and to take care of this several control trunks may be provided, extending to another exchange where `operators are available. One of these control trunks and the associated equipment is shown in Fig. 3.

The control trunk sho-wn comprises the conductors 30| and 30.2. At the manual end the trunk terminates in jack J and associated equipment. At the R, C. X. the control trunk terminates in a link inder F', which has access to all the link circuits. The finder F may also be a single motion rotary switch, and has suflicient sets of contacts to take care of the maximum number of link circuits that maybe provided.

The R. C. X. is also provided with a storage battery, indicated by separate battery symbols in the drawings, for supplying operating current to the switches and relays. Some other source of direct current could, of course, be used. When a storage battery is supplied it is preferably connected to the trunk lines while they are not in use so as to charge from the battery at the main exchange. The connections are shown in Fig. 3, where it will be seen that the R. C. X. battery is connected to trunk conductor 302 at 23|. At the main exchange conducto-r 3l|2 is normally connected to the exchange battery by way of K', and 25B. The R. C. X. battery is preferably a 12-volt battery and since the main exchange battery will have .a voltage of at least 24-volts, a regulating resistance 256 is used to adjust the charging current to the proper value.

It will be assumed now that the subscriber at station A, Fig. l, desires to call the subscriber at station B, Fig. 2. To initiate the call the hand generator is operated. The ringing current energizes the line relay 4, which locks at 5. In operated position, relay Ii marks the associated line in the bank of nder F by ground at E, and at 'I grounds the start lead I4.

The start relay I5 energizes over I4 (23, 52, I5I, I I2, |08), and closes the circuit o1" stepping magnet 28 at I8. The magnet 28 energizes and closes a circuit for stepping relay I6, whereupon relay IE energizes and breaks the circuit of the stepping magnet. The magnet accordingly deenergizes, advances wipers lil-I 3 one step, and breaks the circuit of relay i6, which deenerglzes and again closes the circuit of the stepping magnet. This interaction of 28 and Iii continues and the wipers Ill- I3 are advanced step by step in search of the calling line.

When the test wiper I2 reaches the marked test contact, a circuit is completed from ground by Way of I2, I9, i6, and Ii o battery, which holds relay IS energized to prevent further operation of 23, and -energizes relay i?. Relay I'i locks at 22, and opens the stepping magnet circuit at another point,as relay I5 will shortly be deenergized, due to closure of a circuit from ground at 203 stops the finder.

44 by way of 2| and to line relay 4, which shunts the lower winding of this relay and deenergizes it. The center winding of relay 4 is merely a resistance. The falling back of relay 4 of course breaks the test circuit over I2 and lets I6 fall back. Relay I1 also breaks the start circuit at 23, allowing start relay I 5 to fall back and transfer the start circuit to the finder of the next link.

As additional results of the operation of relay the two line conductors are closed at 20 and 21, the link is marked in the bank of nder F', at 26, and a start circuit for finder F is closed at 25, the circuit extending from ground at |28 by way of |25, |40, 25, 10, 233, and winding of start relay 202 to battery.

On energizing, relay 202 closes a circuit for stepping magnet 204 of nder F. On energizing, stepping magnet 204 closes a circuit for stepping relay 203, and the latter breaks the magnet circuit at 2|9. Magnet 204 and relay 203 accordingly interact and the former advances the wipers 2 I 0--2 I 4 in search of the link in use by the calling line.

When the link is found a circuit is completed from ground by way of 209, 203, 2|8, 2|I, 1|, 25, and 53 to battery, which holds up stepping relay 203 and energizes relay 209. The holding of relay On energizing, relay 20,0 closes the trunk at 23| and 232, and locks itself at 230, the locking'circuit extending from ground by way of 209, 230, 2I4, 15, 42, 54, |4|, and relay |05 to battery. On energizing, relay |05 opens 'the link finder start circuit at |28. Relay |05 also link finder start circuit at 221, allowing start relay 202 to fall back. Relay 203 also deenergizes, following relay 202, as the latter opens the test circuit at 2|8. Relay 209 also closes a circuit for relay 206 at 228. Relay 205 operates relay 205. The latter locks itself and opens the circuit of relay 200, which falls back after an instant, being slow acting. During the interval in which relay 200 is operated, the battery is connected to the trunk conductor 30| at 220. completing a circuit from the battery over 220, 222, 232, 30|, winding of R', K, K', 252, and drop D to ground. The

- drop is thus released to signal the operator.

Answering the call, the operator restores the drop by hand and plugs into the jack J. The cord circuit may be of any suitable and well known type. When the plug is inserted in jack J relays 255, 254, and 251 pull up successively. Relay 255 disconnects the exchange battery from trunk conductor 302 at 25|, connects the trunk conductors together at the same point, and at 253 extends both conductors to battery by way of the calling devic-e key K2. Relay 251 also opens the normal battery connection at 250, and cuts off the drop at 252. This arrangement insures that the exchange battery, normally on the line to charge the battery at the R. C. will be cut off before the dialling battery at the calling device is co..-- nected, so that a higher voltage battery can be used for dialling if desired. Usually, however, the regular main exchange batt-ery will be of high enough voltage. The two slow acting relays 254 and 251 also delay reconnecting the exchange battery to the trunk when the plug is withdrawn.. The reason for this will be explained later.

When relay 255 connects battery to both sides of the trunk, a circuit is completed that can be traced from battery by way of key K2, 253, K', K,. 30|, 232, 222, 220, 2|3, 14, |43, lower left-hand winding of R, contacts controlled by |50, and Winding of line relay |03 to ground. On the clo- Sure of this circuit relay |03 energizes and closes a circuit for slow relay |90, which energizes and. closes a circuit for slow relay I 04. Relay I 04 prepares the operating circuit for connector C at |24, and at |23 closes a circuit for relay |02, which energizes. At ||1 relay |02 breaks the circuit of buzzer relay |06 and closes a circuit for relay 33, at I8 relay |02 disconnects the lower winding of relay |06 from across the line and substitutes the A. C. relay |00. Also at relay |02 closes through the other side of the trunk to the line relay |03 and removes the normal short circuity from the lower winding of differential relay |0I. The line relay |03 is now held energized over a simplex circuit including the two trunk conductors 30| and 302 in parallel. Relay I0! is differentiallyr wound and does not energize. The circuit over trunk conductor 302 parallels the one previously traced over 30| and will be obvious. It may be stated that this circuit is normally open at |50 in order to prevent premature operation of line relay |03 when the trunk is first connected through by operation of relay 209.

Relay 33 energizes when its circuit is closed by relay |02. The opening of contacts 50 and 54 does not deenergize relays II and I 05 because these contacts are now shunted at |22 and |25r of relay |04. Relay 33 also opens a point in the circuit of start relay I5 at 52, and effects certain other circuit changes which need not be noticed now.

It will be observed now that the calling party at station A is in communication with the operator, assuming the latter has thrown the listening key in her cord circuit. The line 2-3 has been extended via Wipers I0 and I3 of finder F and contacts 20 and 21 of relay I1 to the home position contacts which are associated with wipers ||0 and ||3 of connector C. These wipers are connected with the right-hand windings of repeating coil R and the left-hand windings of the repeating coils are bridged across the trunk 30|- 302 through Wipers 2|2 and 2|3 of finder F'. The operator now answers in the usual manner to ascertain the wants of the calling party.

'I'he calling party may or may not have removed his receiver. It may be stated in this connection that although a call is ordinarily ex" tended through to a trunk promptly in the manner described, there exists the possibility of a delay due to the operator being busy or to all links being in use, and the subscribers may be instructed that after putting in a call the receiver need not be removed until the operator calls back. When the operator answers, therefore, if she hears no one on the line she will operate the ringing key in her cord circuit to signal the calling party.

The transmission of ringing current back over trunk line 30|-302 operates the A. C. relay |00, Fig. 2. RelayY |00 closes a circuit for relay 32 which pulls up and makes itself slow acting by short-circuiting its upper winding. This is to guard against possible chattering of relay |00. Relay 32 shorts the condenser at the repeating coil R at 45, which improves the ring-through characteristics of the repeating coil and enables the line relay-4 whichpulls` .up and locksfatfthe beginning of the ringing operation, removingits upper winding` from in bridgeofrfthe line. operation of the line relay. i.. at this .time doesk not start the finder in thenext link because relay 32 closes a circuit for thel commonv relay Gilat t9, and relay 89 disconnectsthe starting v.ground line relay.,lI.,is enabled toA lock .up during ringing because relay 32;rernoves ground from ,wiper IIv at llt. When the ope-rator finishes ringing, one short ring isusually sufficient, relays IUI) ,and 32 fall back, also relay 8,0.` The flatter is slow,- acting so that line relay 4 is shunted down by the closure of 44 beforestarting ground is. again connected up at the contacts of 80.

When the party4 atfstation A. hears his bell ring he will removehis.. receiver and tellthe operator what number he wants. If the. wanted number is that of a subscriber in themain eX.- change the operator. will completethe call in known manner. using the other .end ofthe cord now plugged up .in jack J. There .is nothing in these operations that requires explanation, eX'J cept the fact should be noted that when the con versation is over the subscriber at station A. can

z give a disconnect signal by ringing off according to standard practice. The relays IDU and 321 scriber at station A is able to Aring through andoperate the supervisory relay in thel operators cord. The operation of this relay may'also be usednto recall the operator, as is well known.

When the operatorv pulls down the connection, relay 255 falls back, followed at short intervals by slow relays 254,'an'd'25l.Y Relay '255 discernr nects the dialling batteryffroni'the trunk'linle, breaking the circuit of line relay |93, which falls back and breaks 'the circuit of slow relay |99. Relays ISG, 915,102, and33 now fall back successively. In the interval `between'tli'falling back of relays E04 and` 33 the locking circuit of` relay ll is opened: at Bilanci l2`2,l and relay I 'I falls back. The nder wipers stay where they are, awaiting the next call.. Inthe samel interval between the falling back of relays Inl-i and the locking circuit of relay. 2,09 is opened at 5@ and lt, and relay 2IJ9`deenergizes, also relay IUE. Relay 299 gets back before relay 251 at the main exchange, so the trunk is opened at 231 before the main exchange battery is connected up at 259, which is necessary to prevent reenergization of line relay IBS. In the interval between the falling back or" line relay |93,v and relay i951 an impulse is sent via 49, I2I, and Elfi to stepping magnet IS oi connector C and the. wipers Nill i3 are advanced one step. This prepares the restoring circuit, however, which is completed when relay 33 falls back, the,v circuit extending from ground atV 5l` by way'of IM,v interruptor contacts of Vmagneet |98,- strappedbank contacts, wiper H2, and winding of I to battery. Magnet la operates automatically over the above circuit and drives the connector Wipers to home position. Relay lil] energizes in parallel with magnet i199 and holds up while the "wipers are moving over the banks in order to prevent intere ferencewith the subscribers" lines. The link and trunkline arenowin normal condition or idle Cdn n on... f. `Itfwill`be assumednowthat the subscriber at station' A puts 'infa'call as before described and givesfthe'operator' the number of a local station in` the fR; C. X., thenurnber of station B, for instance, whichis 993. The connector C is a so called adding type connectorand it responds to onetwo, or'three digits to select a desired line. The Contact sets reached by dialling the digit 9 and thetwol digits 99 (see bank of wiper IIB) are resting positionsand'have no lines connected.

When the'operatorreceives the number of the local R, C. X.. station she knows she has to dial backoverfthe'trunk line to complete the connection and therefore she operatesv the dial key K2` associated with the trunk in use. This inserts thefcalling device CD inthe circuit of line relay |93, whiclifis vin energized condition along with relaysIQll," |94, |02, and 33`which it controls.

The operator rnextfdials the three digits of the called number.

Responding to the ilrst digit 9, the line relay |03. deenergizes nine times and sends nine impulses` tothe steppingfmagnet Hi8 which advances' the 4wipers `I IIl--I I3`to the ninth set of contactsfor tothe first resting position. The operatoris disconnected from the calling line as soon as wipers IIIiand IIS leave home position. Relay Illoi course holds on during dialling. Relay lt'Voperates to open circuit wipers I III and I I I Aat, |29, and |39 and prevent interference with lines mornentarily, contacted during movement of thefwipersl On'the second digit 9 the line relay and magnet |98 advance the wipers to the second resting position, and on the third digit 3 the wipers arevadvanced to the setof contacts associated with the line of station B, as can be seen clearly?, from the drawings.'

vThere is no automatic busy test; but the operator, having completed dialling and restored lier key K2, listens on the lineand then challenges if necessary to ascertain if the line is busy or not. It will beassum-edrst that the line is busy.

Having ascertained that the called line is in use, the operatoractuates key K for several seconds, or long enough to give the connector C plenty of time to restore. The operation of key K opens one side of the trunk and the line relay i209 holds'over the` other trunk conductor alone. Also onewinding of differential relay lill gets no current, andthe relay operates on the other winding,V closing a circuit for relay 3ft. The latter relay closes the homingcircuit oi the connector Cirom ground at 5l by way of 55, 5l, lflll, interrupter contactsof magnet IESS, wiper H2, and winding or rnagnet lil to battery. When the switch cornes to rest in home position the trunk isy again connectedfto the calling line through wipers H9 and IIS, and the operator can inform the calling party at station A that the called line is busy. v Ii the operator withdraws lier plug from Jack J now the link and trunk are restored to normal, as previously explained;

Returningnow to the point where the called line 993 was connected with, it will be assumed that the line is found to lbe idle. The operator then actuates her ringing key, transmitting ringing current over the trunk line and through the connector wipers 'H9 and H3 to the called line. Contacts 39 and 4,3 of relay 3l are shunted by small condenser/s which vpermit enough ringing current to leak back to the calling line to give the calling party the usual ringing signal. The ringing operation is similar to the ringing operation already described in connection with station A. Relays |00 and 32 respond, and the latter relay short circuits the condenser in repeating coil R and also removes ground from wipers III of the connector. The latter operation enables line relay 4' to respond at the first application of ringing current and clear itself off the line. Relay 80 is also energized to prevent relay 4 from starting a finder when it energizes. When relay 32 falls back at the end of the ringing operation, relay 80 restores, and the line relay 4 is shunted down again. The operation of relay 32 produces a further result in this case due to connector C being off normal. Each time relay 32 energizes it operates relay 35, but the operation of the latter relay is of no consequence unless the connector C has been operated, in which case relay 35 locks up over a circuit which extends from ground at IIS, |45, lower winding of 35, 56, |44, interrupter contacts of magnet |08, wiper I I2, and winding of magnet |08 to battery. In operated position relay 35 prepares a circuit for relay 3| at 51.

Having iinished ringing, the operator brings about the final connection of the calling and called lines by momentarily operating key K. This key opens one side of the trunk line and permits relay |0I to energize as previously ex-V plained. Relay |0I operates relay 34, which closes a circuit for relay 3| at 55', since relay 35 is now energized. Relay 3| energizes, locks itself at 38, and connects the calling and called lines a't 39 and 43, At 40 relay 3| opens the impulsing circuit, and at the same point closes a circuit for relay |04. At 42 relay 3| opens a point in the locking circuit of relay |09, but the circuit is not opened because contacts 42 are now shunted by contacts |9| of relay |90.

The operator may now Withdraw her plug from jack J, which disconnects the dialling battery from the trunk and breaks the circuit of line relay |03. Relay |03 and slow relay |90 accordingly fall back, but relay |04 stays operated due to the circuit now closed at 40 by relay 3|. When relay |90 falls back it opens the shunt around contacts 42 at I9I, and thus breaks the locking circuit of relay I 09, which falls back and restores the trunk to normal condition.

When the subscriber at station B answers his telephone the conversation can go ahead. The talking circuit is a full metallic circuit without inductive connections in the link. When the sub- 'scribers are through talking they hang up their receivers and ring off as is standard practice. The ringing current operates relay |00, which operates relay 32, as previously explained. Relay 32, since relay 3| is now energized, closes a circuit for relay 30 from ground at 48 by way of 38 and 41. Relay 30 energizes and opens 36, but relay 3| stays locked to ground at 48. When the ringing ceases relays |00 and 32 fall back, with the usual results. Also relay 32 breaks the circuits of relays 3| and 30 at 48. Relay 30 is slow acting so relay 3| gets back rst and opens its locking circuit at 38 before it can be closed at 36. When relay 3| deenergizes it breaks the circuit of relay |04 at 40. The deenergization of relay |04 is followed by the deenergization of re` lays |02, 35, 33, and I1, and the link is restored to normal. Relay 33, it will be noted, closes the homing circuit of connector C at |.Y

If the subscribers failto ring oi the link is released by the timer T.- When relay 3| energizes it closes a circuit for the timer at 31. The timer is a thermostat, adjusted to close its contacts after a predetermined interval such as ve minutes. When the timer operates its contact it closes a circuit for relay 30, which unlocks relay 3| and the link is restored as previously explained.

It will be assumed now that the operator receives a call from a subscriber in the main exchange who desires to be connected with a station such as B in the R. C. X. To complete this connection the operator plugs into a trunk jack such as J, which operates the associated finder such as F to connect with an idle link in the R. C. X., and the operator then dials the connector of the link on to the desired line.

When the plug is inserted in jack J, relays 255, 254, and 251 operate as already explained, with the result that the normal charging circuit is opened, the drop is cut off, and the dialling battery isconnected to both conductors of the trunk line. Battery being connected to trunk conductor 30|, an obvious circuit is completed for relay 201, which energizes, locks itself on to the trunk at 224, and opens both sides of the trunk at 222 and 223. A circuit is also closed for relay 208, the function of which is to prevent the subsequent energization of relay 209 from operating relays 205 and 206. Finally, relay 201 closes a circuit for start relay 202 at 226, and prepares the test circuit at 225.

Consideration should now be given to the fact that all the links at the R. C. X. may be busy, in which case the nder F' would not be able to find an idle link. Each link has two terminals such as 82 and 83, Fig. 1, which are included in a chain circuit. At the rst link terminal 82 is connected to ground and terminal 83 is connected to terminal 82 of the next link. Terminal 83 of the second link is connected to terminal 82 of the third, and so on, except that terminal 83 of the last link is connected to a common relay 200. Nowif allthe links are in use the chain circuit will be completed, for in each link contacts such as 24 or |20, or both, will be closed, and relay 200 will be energized. Relay 200 opens the circuit of start relay 202 at 2|5, or rather prevents this circuit from being closed at 226 by the operation of relay 201. Relay 200 also sets the buzzer relay 20| in operation, and connects the upper Winding of such relay to the trunk, whereby a tone current is transmitted over the trunk to the operator to inform her that no links are available. The operator can then wait on the trunk until the tone disappears, as it will do when a link becomes idle, or she can withdraw her plug and tell the calling party to call again.

Assuming now that the link shown in Figs. 1 and 2 is available for use, the common relay 200 will not be energized when the operator plugs into the trunk, and when start relay 202 operates it will close the circuit of the stepping magnet 204 at 2|1. The stepping magnet 204 and stepping relay 203 now interact as previously described and the former begins to step along the wipers 2|0-2|4. The idle condition of the link is denoted by the presence of battery potential on conductor 12 by way of 26 and 53. When the nder wipers reach the link shown, therefore, assuming this is the first one found idle, wiper 2|0 will pick up the battery potential, closing a circuit for holding stepping relay 203 and energizing relay 209. Holding up relay 203 stops the iinder F' by holding 2|9 open. Relay 209, on energizing, locks itself in series with relay |05 in the link, as previously explained. Relay |05 makes the link busy to local subscribers by open- With -results previously'explained.

ing the circuit of start relay I at l5l. Relay 2,09

shifts its contacts 23| .and 232, but the trunk is not extended through because relay `201 is still energized. It willbe noted that the latter re- Ylay is not cut oiffrom thevtrunk at 232 because it is locked at 224. Relay 209 also closes a locking circuit for relay 208, to prevent this relay from falling back When relay 201 deenergizes. Also the circuit of start relay 202 is broken at-229 and the transfer of -the starting circuit takes place at 221.

The R. C. X. battery is normally bridged across the trunk line through relay 201, but is cut off at 23| when relay 209 pulls up. This produces a click inthe operators receiver which is recognized by her as. a signal that an Lidle* link vhas been found. To seize the -link the operator `now momentarily operates key K. This disconnects :battery from ccnductor'Sl andpermits relay `201 to drop back. Relay 201 cuts itself off from the trunk at 224 so .that it cannot energize again when the key is restored, andcloses the trunk through at.222 and 223. The line relay I03does not energize over conductor 302 because this side of the simplex control circuitis open at..|50.

vWhen key K is restored the dialling battery is reapplied to conductor30i Vandthe'line relay w3 energizes. Following the-operation of the line relay, relays |00,-!011, |02, and 33 pull'up, It may be mentioned, however, that the opening of contact 53 of relay-33 makesV the'link busy to another finder .such as F that might be started up by the operator. Y

The equipmentis now ready for dialling to begin, and the operator may operate her dial key KZandthen operate the calling device CD in accordance With the number of station B or. any other station. 'I'he operation of the connector C responsive to dialling'has already been described and it will not be necessary togo over'thisagain, nor to explain how the link andtrunk are restored, as this has also been explained before.

The key K which is associated with the trunk line along with keys K and K2 is not strictly necessary, but may be supplied as a convenient means-for clearing both sides of the trunk of battery and ground connections.

The system herein described is primarily intended for/individual line service, but neverthef,

less it is capable of handling party lines with a limited number ofstations -on each line. The line of station B is therefore indicated as having a second station B. The stations on a party line can `signal each other by code ringing with their-hand generators and-sofar as this phase ofthe system operation is concerned there could be the usual number of stations on each line. The `limit is imposed by the fact that on calls from the main exchange to the R. CfX. the operator has to ring through the repeating coils R and R, and with repeating coils. now in general use the ringing current at a connected line being signalled from the main exchange is inadequate to satisfactorily operate more than three or four ringers. 'Ihe number of stations on a line `therefore should not ordinarily be greater than four. When a party line subscriber rings anothersubscriber on his own line he of courserings up his line relay such as 4 at the same time, which brings the, call in to the operator at the main exchange. It is usually preferable, therefore, to instruct party line subscribers to'calltheoperator for every connection 1 even though a party on the same line is desired.

f At the same time, in an emergency, such as would existir vthe links were all busy, the hand generator methodof code ringing is available and can be used.

-Theinvention having been described, that which is believed to be new and for which the protection of Letters Patent is desired will be .pointed-out in the-appended claims.

What is claimed is:

l. In a telephone system, a rst exchange,

links inthe first exchange, each comprising a finderand a connector, trunks leading from the first exchange` to a second exchange, each. trunk terminating at the first exchange in a finder which has access tosaid links, means for setting up a connection from the first exchange to the second by operating successively the finder of an idle linkfand the finder of an idle trunk, and

.link and any trunk, meansfor setting up connections` from the second exchange tothe first by Way of any trunk and the connectorroi' any link, the` link connectors being excluded from the former connections and the. link nders from f the latter, means for setting up connections local to thevfirst exchange by Way ofthe nder and connector of any link, and means for controlling the establishment of local connections over any Y trunk.

l 3. In a telephone system, a plurality of links -forconnecting calling and called lines, a plural# ity of trunk lines associated with said links and extending to an operators position, means responsive to a call for connecting an idle link and =an-idle trunk, means forextending the, call to the called line responsive to directive impulses transmitted over the trunk, said means including a line relay in the link responsive to said impulses, means for imposing a control condition on-the trunk to which the line relay is non-ree sponsive, and means responsive to said control conditionfor completing the call through the link and for disconnecting the same from the trunk.

4,-In a, link circuit, a nder, a connector, and circuits over which the finder wipers are con nectedA to the connector Wipers through bank contacts normally engaged by. the connector Wipers.

5. In a link circuit, a finder, a connector, means includingthe` home position bank contacts of the connectorfor connecting the finder @wipers with thev connector Wipers before the connector is operated, and relay contacts for connecting the finder wipers with they connector wipers after ther connector is operated.

6. In a telephone system, a link comprising a Y nder and a connector, a trunk, and circuits for connecting the finder Wipers with the trunk by -Way of .the `connector Wipers and contacts normally engaged thereby.

'7..In atelephone system, a link comprising a finder and a connector, means .for operating said finder to connect With a calling line, a trunk, means responsive to the completion of the connection to the calling line for connecting said trunk to the wipers of said connector, and circuits leading from the wipers of the nder to normally occupied contacts in the bank of the connector, whereby the connected calling line is extended to said trunk.

8. In a telephone system, a link comprising a nder and a connector, a trunk, means for connecting said trunk with a calling line through wipers of the connector and finder in serial relation, and means for connecting the trunk with a called line through wipers of the connector alone.

9. In a telephone system, a link comprising a finder and a connector, means for operating said iinder to connect with a calling line, a trunk, means for connecting the trunk with the link, means for operating and restoring said connector over the trunk at will while maintaining the trunk connected to the link, and circuit connections over which the trunk is connected to a called line when the connector is operated and to the said calling line when the connector is restored.

10. In a telephone system, a link comprising a iinder and a connector, a trunk, means including the nder in operated position and the connector in normal position for connecting a calling line with said trunk, means for operating the connector over the trunk to connect with a called line, thereby breaking the connection between the trunk and the calling line, and means controlled over said trunk for restoring said connector to reestablish the connection between the trunk and the calling line.

11. In a telephone system, a switch, a control circuit for said switch including the two sides of a line in parallel, means for operating said switch responsive to momentary interruptions of both sides of said line, means for interrupting one side of said line while maintaining the other side closed, and means responsive to such interrupting of only one side of the line for restoring said switch to normal.

12. In a telephone system, a link comprising a finder for connecting with a calling line and a connector, a trunk associated with said link, means for controlling said connector over said trunk to connect with a called line, a relay in the link responsive to ringing current received over the trunk, means for imposing a characteristic control condition on said trunk, and means responsive to said control condition for establishing a talking connection through said finder and connector or for restoring the connector, depending on whether said relay has been operated or not.

13. In combination, a line, a line relay at one end of the line normally connected to only one conductor thereof, whereby the line relay will not respond when a current source is connected to the other conductor, means for connecting a current source to both conductors of the line at the end remote from the line relay, thereby energizing the line relay over the conductor to which it is connected, a slow acting relay controlled by said line relay and held in operated position during momentary deenergizations of said line relay, and means' including said slow relay for connecting said line relay to the conductor from which it is normally disconnected, whereby the line relay may be controlled from the said current source at the remote end of the line over both conductors of the line in parallel.

14. A dialling circuit including the two sides of a line in parallel, means for connecting a current source to both sides of said line at one end, a line relay at the other end initially energized over only one side of the line, and means controlled by said line relay while the same is energized or only momentarily deenergized for including the other side of the line in its energizing circuit.

15. In combination, a trunk line, a line relay connected to the first conductor at one end, means at the other end for connecting a current source to both conductors, thereby energizing said line relay, a double wound differential relay, a slow-acting relay controlled by said line relay, means including said slow relay for connecting said line relay to the second conductor of said line and for connecting the two windings of said differential relay in the two conductors of said line, respectively, in series lwith said line relay, and means for interrupting the connection of said current source to one of said conductors, whereby the line relay is maintained and the differential relay is operated over the other conductor.

` 16. In a telephone system, a ringing circuit including a trunk line and a subscribers line, a repeating coil included in the connection betweenthe trunk line and the subscribers line, control circuits superimposed on said trunk line and requiring a condenser to be included in series with the repeating coil windings which are connected to the trunk line, a relay associated with the repeating coil and responsive to ringing current when the ringing circuit is used, and means including said relay for short circuiting said condenser to give the repeating coil the necessary ring through characteristics.

1'7. In a telephone system, a subscribers line, a relay bridged across said line and responsive to ringing current coming from the station on said line or from the exchange, switching apparatus controlled by said relay, and means for preventing said relay from controlling said apparatus if it is operated by ringing current from the exchange.

18. In a telephone system, a subscribers line, a line relay for said line responsive to ringing current when the line is calling to start a iinder, said relay also responsive to ringing current when the line is called, and means for preventing said relay from starting a finder when the line is called.

19. In atelephone system, a plurality of links, each including a iinder for connecting with calling lines, means in each link for connecting with called lines, means for ringing connected called lines, means common to said links for preventing the operation of the said iinders, and means in each link effective while a called line is being rung from such link for rendering said common means effective.

20. In a telephone system, an automatic exchange, a group of links for completing local calls in the exchange and for completing calls incoming from another exchange, a group of trunks incoming from said other exchange, each trunk terminating in a. finder having access to said links, means controlled from a link when the same is in use for a local call for starting the nder terminating an idle trunk and causing such finder to find the link, and means controlled over a trunk on an inter-exchange call for starting the finder associated therewith and for causing the same to find and connect with an idle link.

EDWARD S. PETERSON. NORMAN H. SAUNDERS. 

